Group III nitride crystals are suitably used in semiconductor devices such as light-emitting devices and electronic devices. To reduce the cost of such group III nitride crystals, group III nitride crystals having a large size have been demanded.
Since group III nitride crystals that have a large size are not found in nature, group III nitride crystals are grown on substrates (base substrates) that are composed of materials represented by chemical formulae other than those of group III nitride crystals. For example, Japanese Unexamined Patent Application Publication No. 2000-349338 discloses a method for growing a group III nitride (GaN) crystal film having a large thickness without warping or cracking on a substrate (base substrate) that is composed of a material represented by a chemical formula other than that of the group III nitride crystal.
However, it is difficult to grow a group III nitride crystal having a sufficiently large size by the method disclosed in Japanese Unexamined Patent Application Publication No. 2000-349338. This is because, when a base substrate has a large main surface area, crystal lattice mismatch between a group III nitride crystal and the base substrate increases distortion within the group III nitride crystal and, as a result, the crystal warps or cracks.
To address such a problem, Japanese Unexamined Patent Application Publication No. 2008-133151 discloses a crystal growth method including a step of arranging a plurality of seed substrates such that sides of the seed substrates are adjacent to each other and a step of growing group III nitride crystals on the surfaces of the plurality of seed substrates by a hydride vapor phase epitaxy method (hereafter, abbreviated as an HVPE method) such that the crystals are integrated.